Tumor motion modulates dose delivery in radiation therapy, often resulting in uneven dose distribution across a target region. Dose modulation may be caused by an interplay between the moving parts in a radiation therapy system (e.g., the multi-leaf collimator (MLC), the movable gantry upon which the therapeutic radiation source and the MLC are mounted, the patient platform, etc.) and the motion of the tumor. For example, because lung tumors are subject to a large range of motion that result in the tumors moving into and out of the treatment plane unpredictably, it can be challenging to deliver the prescribed radiation dose to the tumor.
Several solutions have been proposed to mitigate unwanted dose modulation. One solution for a tomotherapy machine with a rotatable gantry is called dose painting and involves arcing the therapeutic radiation source over the patient treatment region twice at a particular couch location. That is, first moving therapeutic radiation source in the clockwise and then in the anti-clockwise direction. Dose painting methods may reduce the variability in the dose delivered, but at the cost of increased treatment time. Other solutions for motion management and dose artifact reduction include coached breathing, breath hold, and respiratory gating. Instructing the patient to hold their breath during a radiation beam pulse may help limit the range of motion for the tumor, but depending on the health of the patient, it may not be possible to ensure consistent breath hold. Improved systems and methods for ensuring the uniform delivery of radiation dose to a moving target region are desirable.